Author(s): Jadhav SP, Kamath SP, Choolani M, Lu J, Dheen ST
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Abstract Chronic activation of microglia, the macrophages of the CNS, has been shown to enhance neuronal damage because of excessive release of proinflammatory cytokines and neurotoxic molecules in a number of neurodegenerative diseases. Recent reports showed altered microRNA (miRNA) expression in immune-mediated pathologies, thus suggesting that miRNAs modulate expression of genes involving immune responses. This study demonstrates that miRNA-200b is expressed in microglia and modulates inflammatory response of microglia by regulating mitogen-activated protein kinase pathway. miRNA-200b expression was found to be down-regulated in activated microglia in vivo (traumatic brain injury rat model) and in vitro. A luciferase assay and loss- and gain-of-function studies revealed c-Jun, the transcription factor of cJun-N terminal kinase (JNK) mitogen-activated protein kinase pathway to be the target of miR-200b. Knockdown of miR-200b in microglia increased JNK activity along with an increase in pro-inflammatory cytokines, inducible nitric oxide synthase expression and nitric oxide (NO) production. Conversely, over-expression of miRNA-200b in microglia resulted in a decrease in JNK activity, inducible nitric oxide synthase expression, NO production and migratory potential of activated microglia. Furthermore, miR-200b inhibition resulted in increased neuronal apoptosis after treatment of neuronal cells with conditioned medium obtained from microglial culture. Taken together, these results indicate that miRNA-200b modulates microglial inflammatory process including cytokine secretion, NO production, migration and neuronal survival. © 2014 International Society for Neurochemistry.
This article was published in J Neurochem
and referenced in Journal of Addiction Research & Therapy